The invention relates to a device and process for handling strip-shaped products in order to use them to make a cover.
To make a cover of this kind, various different products are used, and these are initially stored in the form of continuous strips wound onto storage bobbins arranged in supply stations. These strips are unwound and then cut into sections of predetermined length. The various sections are then wound around a building drum by being deposited one after the other.
Moreover, once some pairs of products are laid on the building drum, they are symmetrical with respect to a plane perpendicular to the axis of rotation of the drum and passing through the centre of the drum. If the intention is to obtain the two sections from a single strip coming from a single supply station, then before depositing one of the two product sections onto the drum it has to be pivoted by 180° about an axis perpendicular to the plane of this same product section, which is laid flat, to obtain a section which is symmetrical with respect to the section which does not undergo this pivoting. Once they are deposited, one after the other, on the left-hand and right-hand sides of the building drum, the two product sections then have the desired symmetry.
The products referred to above may be rubber profiles, rubber strips or indeed plies formed from a rubber mix in which textile threads or metal cords are embedded, arranged parallel to one another and forming a defined angle with the longitudinal direction of the ply, these plies being called for example “carcass reinforcement plies” or “belt plies”, depending on their position within the tyre.
Taking into account in particular the large number of different products to be laid, the mass and volume of the ply sections, when making tyres of large dimensions, such as those intended for construction machinery or agricultural vehicles, most of the operations (comprising unwinding continuous strips from their respective supply stations, cutting them off to form sections, turning them and transferring the said sections to the building drum) remain manual to date and are somewhat onerous.
To automate these operations and to improve ergonomics, a large number of technological solutions may be implemented.
Thus, it is possible to envisage the cooperation of a laying drum, which is movable in the direction transverse with respect to the direction in which the products are unwound and comes into position on demand along the axis of servers, which are generally fixed, each comprising a strip-unwinding system, with a cutting system and a transfer system. These principles are disclosed for example in U.S. Pat. No. 3,654,828.
However, this solution has the result that the number of cutting and transfer systems are multiplied, which substantially increases the cost of an installation of this kind. Another approach, which is particularly advantageous, consists in installing one or more movable assemblies carrying out the cutting and then the transfer of the strip sections from the fixed unwinding stations of each of the products to a fixed laying drum. A description of this kind of device can be found, by way of example, in U.S. Pat. No. 4,504,337.
Because of the great length of the sections to be handled, these transfer assemblies generally make use of storage cylinders around which the section to be transferred is wound before being deposited on the laying drum. Cylinders of this kind, which may be fixed or movable, are disclosed in DE 27 40 609, U.S. Pat. No. 3,591,439 or indeed U.S. Pat. No. 3,654,828. The product is kept wound around the outer surface of the cylinder either by a pneumatic device establishing a negative pressure between the sole of the product and the surface of the cylinder or by a set of electromagnetic devices, where the products contain metal elements.
However, these systems are ill suited to handling sections of several meters weighing several tens of kilos, as is often the case for making tyres intended for construction machinery or agricultural equipment. Moreover, the products whereof the final positions on the drum are symmetrical, are unwound from two separate supply stations, which tends to increase the number of stations and the size of the installation.
The object of the invention is specifically to find a solution which is highly flexible to use in the handling of strip sections of great mass and length.